Magnetic characteristics and trace elements concentration in soils from Anthemountas River basin (North Greece): discrimination of different sources of magnetic enhancement

摘要

The magnetic minerals (e.g., iron oxides) that are present in soils can be easily identified by using rock-magnetic techniques. Increased magnetic susceptibility of soils may reflect particles rich in iron oxides of anthropogenic, lithogenic, and pedogenic origin. Therefore, reliable discrimination of these sources is required, especially in areas where neither of them is dominant. The aim of the present study is to assess the lithogenic and anthropogenic contributions to iron-oxide mineralogy of soils in the area of the Anthemountas River basin in the southeast part of Thessaloniki city. Previous investigations within the study area, based on spatial distribution of magnetic susceptibility, revealed the presence of two magnetically enhanced regions. Therefore, the present study is focused on these two areas, in order to characterize the origin of magnetic enhancement. Detailed magnetic analyses include properties reflecting the type, concentration, and relative grainsize distribution of magnetic particles. Moreover, trace element concentration is determined with an aim to establish the link between low-field mass-specific magnetic susceptibility and concentration of Fe, Cr, Ni, Mn, Pb, Zn, and Ti. These findings are supported by descriptions of the micromorphology performed by scanning electron microscopy and determination of elemental composition by energy-dispersive spectrometer analyses in selected points. Finally hierarchical cluster analysis is applied to classify the soil samples into appropriate groups according to their magnetic properties. The results reveal that magnetic measurements provide a useful tool for the discrimination between different magnetic sources responsible for the enhancement of magnetic susceptibility in soils. Low-field mass-specific magnetic susceptibility reflects increased concentration of trace elements, while its combination with other magnetic measurements clearly differentiates the origin of magnetic enhancement in both parts of the study area.